Extruded thermoplastic profiles are commonly used in every sector of human life. Extruded profiles are usually supplied in linear form. Currently bending of extruded profiles such as plastic pipes or arched plastic window frames is done in post-extrusion environments where a pre-determined length of linear-shaped profile is re-heated and gradually bent into a desired shape. Such methods of bending and shaping of profiles are labor intensive and therefore costly, and limit profiles utility. Production costs further increase if some level of complexity is introduced in the geometry of the profile.
Spiral welding machines for wrapping a hot strip of metal or plastic material around a constant-diameter coiler to form a pipe or a tank are known technology. However, wrapping a bulky profile of complex cross-sectional geometry around a mold of uneven geometry (rectangular, triangular, trapezoidal) and maintaining continuously the inner and outer cross-sectional dimensions of that same bulky profile substantially constant during bending so that the walls of the profile do not collapse has been a challenge. Furthermore, accomplishing all the above activities in an economic manner is an even greater challenge.
Accordingly, it is desirable to develop a cost-effective apparatus and method for bending and shaping extruded thermoplastic profiles, preferably inline with an extrusion process. It is also desirable that the method accommodates all profile configurations and all types of malleable products ranging from thermoplastics to organic minerals that are extrudable and that can solidify outside the extruder under the effect of cold, heat, or chemical treatment.
To address some of these requirements, Rowly disclosed in U.S. Pat. No. 6,838,041 a post-formation processing method for extruded or injection molded profiles requiring the sealing of one end of a tubular object, applying internal pressure from inside and creating a vacuum from the outside. Similarly, Klein disclosed in U.S. Pat. No. 6,129,885 a post-extrusion method using a combination extrusion and blow molding method to impart a shape to a pipe-shape profile. Archmaster, a company with a website (http://archmaster.eu)—visited on Dec. 22, 2006—disclosed manually operated equipment for bending profiles. Archmaster uses—as shown in the attached drawing labeled FIG. 10 (hereinafter “figure ten”)—multiple flexible plastic blocks that are fitted around a profile to protect the profile's cross-sectional deformations during bending. This manual post-extrusion method is slow and labor intensive. Another company Pipe Coil Technology Limited with a website (www.pipecoil.co.uk/html/plumbing.htm)—visited on Dec. 22, 2006—disclosed a coiling solution for plumbing pipes. Another company named Pipestar International offers on the internet at www.arcbends.com, pipefittings, and sweep bends. Pipestar uses a post-extrusion process involving the heating of a fixed-length linear pipe and uses jigs to bend it.
While prior art provides a partial solution to the problem of bending thermoplastic profiles, the prior art suffers from the disadvantages of providing only post-extrusion methods that are all labor-intensive and are limited in the ability to bend thermoplastic profiles of complex geometries in a cost-effective manner.